A piece of hard, 5/16-inch square balsa is
trimmed to fit across (at the horn side of the
servo) and under the skin, then lightly glued
to the skin and the servo with Shoe Goo or Zap
glue so it can easily be removed.

This MKS servo is new and has been specifically developed and
designed for composite model sailplane aileron and flap control. It has
many features not included with other servos available today. Photo
used with permission from MKS Servos USA.

Deadly flutter and how to avoid it

by Gordon Buckland

gordon@gatorf3b.com

Have you seen a beautiful sailplane on tow suddenly break apart? The model probably appeared
to be perfect and had been launched
dozens of times before without
any issues. This time, it seemed to
disintegrate on tow.

We sometimes hear a sailplane
make an unmistakable machine gun-like fluttering noise as the pilot puts
it through the “bucket.” The modeler
is able to save the dying airframe by
heroically landing it on flaps minus
ailerons or elevator control (or both).
The model sometimes only suffers
wiper damage, aileron servo failure, or
broken control horns. Sadly, we have all
likely seen models destroyed during or
after one of these towing incidents, and
watched as the aircraft crashed back to
terra firma.

I have heard pilots attempt to blame
the manufacturer, saying, “The model
wasn’t built right,” or “the stabilizers
weren’t made strong enough,” etc.

The truth is that competition has
driven manufacturers to make models
lighter, while maintaining the necessary
strength to endure hundreds of highly
stressful launches and bone-jarring spot
landings.

Sometimes,
on very rare

occasions,
models do
blow up
because of a
manufacturing
anomaly
or mistake.

Occasionally,
insufficient
resin might
be used when
the molds
are closed,
the skin, or a leading edge could open
up through insufficient resin when
assembled. This can happen, but in
my experience it is rare. The culprit
responsible for your model fluttering
and disintegrating is generally not the
airframe manufacturer.

The root cause can also be
attributed to wear and tear and lack of
maintenance. Sometimes it is simply
poor building techniques and lack of
attention to the details. That is what
this month’s column is about.

Attention to Details

Most of us are meticulous when
we build a model and first fly it.

We take great care to ensure that
the installation of the electronics is
perfect and we prepare and fly our
new airplanes carefully during that all-important maiden flight.